The liquid crystal display (LCD) device is classified by difference in driving methods for a passive matrix type and an active matrix type.
The active matrix type is provided with active elements such as transistors or diodes for each pixel, and these elements are successively selected in a time-divisional mode to turn on them so as to charge the capacitance formed for each pixel, with applied signal voltage, while holding the signal voltage in the capacitance during the period of turn-off state. This active matrix type has the feature that the large-volume indication is possible with high contrast compared with the passive matrix type which apply voltage to the liquid crystal with a time-divisional matrix driving method.
As for the operation mode of the liquid crystal in  the active matrix type LCD device, the twisted nematic (TN) mode has been used conventionally. This TN mode is used for a display by rotating the direction of the molecular axes of the liquid crystal molecules (hereinafter, referred to as the director) in the vertical direction with the vertical electric field to the substrate by rotating the director about 90 degrees between the upper and lower substrates so as to achieve the twist orientation of the liquid crystal molecules.
However, this TN mode has a problem that a viewing angle is small. Therefore, in a certain mobile use of seeing from the various directions, the indication from the oblique direction cannot be visually recognized any more. When the large-volume display is developed and the screen area becomes large, when the screen is judged from a viewpoint in an oblique direction, observation feature is different in the middle of the screen and the screen edge, and a proper display becomes impossible.
To this end, an in-plane switching (IPS) mode and a fringe field switching (FFS) mode have been developed. In these switching modes, the display operation is performed by rotating the director in the horizontal plane by generating the electric field in the parallel direction to the substrates. In such driving modes, wide viewing angle can be achieved compared with the LCD device of the TN mode, even if the viewpoint is changed, because the birefringence of the liquid crystal does not change greatly owing to that the liquid crystal is oriented in the horizontal direction. 
The LCD device is adopted for display screens of the cellular phone appliances, personal digital assistants (PDA) and the business-use terminals in view of such features of light-weight, thin type and low power consumption. Although such LCD devices enable an excellent display at dark places and those places in less bright, there are some situations affected by such ambient light as sunny outdoor arid bright offices to degrade its visibility greatly and results in difficulty for confirming the display on the screen. In order to resolve such problems, a reflective type LCD device and a transflective LCD device have been developed. The reflective type LCD device enables its display by reflecting the ambient light with a reflector as a light source. On the other hand, the transflective LCD device can perform both of the reflective type display and the transparent type display by dividing the pixel into the reflective area and the transmissive area.
The transflective LCD device with the transverse electric field system is disclosed in such documents as Japanese Patent Application Laid-Open No. 2007-41572 (patent document 1), Japanese Patent Application Laid-Open No. 2007-322941 (patent document 2), and Japanese Patent Application Laid-Open No. Hei-11(1999)-174491 (patent document 3).
The LCD device disclosed in the patent document 1 is the transflective LCD device in which the transmissive areas and the reflective areas are provided in each pixel for the IPS mode. Its structure is shown in FIG. 26 through  FIG. 29. FIG. 26A is a plan view showing the structure of the transflective LCD device in a structure when a reflector is removed, FIG. 26B is a plan view showing a structure added with the reflector, and FIG. 26C is a plan view showing a structure which is further added with a black matrix layer. FIG. 27A shows a cross-sectional structure along the XI-XI line shown in FIG. 26C. FIG. 27B is a cross-sectional structure along the XII-XII line shown in FIG. 26C, and FIG. 27C shows a cross-sectional structure along the XIII-XIII line shown in FIG. 26C. FIG. 28 is a schematic drawing indicating the structure of the wirings and electrodes of one pixel. FIG. 29 is a drawing showing the waveforms of the transmissive common signal and the reflective common signal.
As shown in FIG. 26 to FIG. 29, the LCD device disclosed in the patent document 1 is provided with a plurality of scanning lines 12, signal lines (data lines 13) and common electrode lines which are arranged in a matrix shape on a transparent insulating substrate (hereinafter, referred to as a TFT substrate 10) in which thin film transistors (TFTs) are formed. Each of the common electrode lines includes a transmissive common electrode line 18a which applies a reference potential to a transmissive area 3 and a reflective common electrode line 18b which applies a reference potential to a reflective area 2. A transmission-TFT 14a for a transmissive pixel electrode 17a in the transmissive area 3 of each pixel are respectively arranged at upper section in each intersection of the scanning lines 12 and the data  lines 13. On the other hand, a reflection-TFT 14b and a reflective pixel electrode 17b corresponding to the reflective area 2 of the pixel are respectively arranged at lower section in the intersection of the scanning lines 12 and the data lines 13. The transmissive pixel electrode 17a is connected to a source electrode of the transmission-TFT electrically via a contact hole 170a while the reflective pixel electrode 17b is connected to a source electrode of the reflection-TFT electrically via a contact hole 170b. 
A transmissive common electrode line 18a is connected to a transmissive common electrode 18a′ electrically via a contact hole 180a while a reflective common electrode line 18b is connected to a reflective common electrode 18b′ electrically via a contact hole 180b. 
The transmissive pixel electrode 17a and the transmissive common electrode 18a′ are provided so that both electrodes 17a and 18a′ are arranged in parallel each other like stripes. As a result, the electric field is generated at the transmissive area such that the main component of the electric field crosses the both electrodes at right angle and parallel to the substrate surface. The reflective pixel electrode 17b and the reflective common electrode 18b are provided so that both electrodes 17b and 18b′ are arranged in parallel each other like stripes. As a result, the electric field is generated at the reflective area such that the main component of the electric field crosses the both  electrodes at right angle and parallel to the substrate surface.
In the reflective area 2, a reflective plate or film (hereinafter, referred to as a reflector 16) is provided under the reflective pixel electrode 17a and the reflective common electrode 18b′ via an insulating film 15b. 
According to the patent document 1, in the transflective LCD device using the IPS mode, the transmissive area 3 assumes a normally black mode, wherein the transmissive area 3 represents a black display upon absence of an applied voltage whereas the transmissive area 3 represents white display upon presence of the applied voltage. On the other hand, because the reflective area 2 assumes a normally white mode, wherein the reflective area 2 represents a white display upon absence of the applied voltage whereas the reflective area 2 represents the black display upon presence of the applied voltage, the transmissive common signal and the reflective common signal need to reverse its phase each other as shown in FIG. 29 when the identical video signal is used.
In that case, the different electric potentials are applied respectively between not only to adjacent pixels but also to the transmissive area and the reflective area within the pixel. Accordingly, the electric fields unrelated to the display are generated among them, and the light leakage caused by those unrelated electric fields occurs. Accordingly, in order to prevent the light  leakage, such shading structure is generally used in the LCD device that a film of metals such as chrome or a laminated film of those oxidized metals, or a layer of black matrix 22 made of resin or the like dispersed with carbon particles.
In the case of using the active matrix type LCD device of the TN mode, such electric fields affecting the display is not generated any more in any electric potentials, because the electric field toward the black matrix 22 on the opposed substrate 20 is electrically shielded by a transparent electrode formed on the opposed substrate 20 close to the liquid crystal surface side.
However, the active matrix type LCD device with the IPS mode as shown in FIG. 27 somewhat affects a display. This is because a shielding electrode like the transparent electrode used for the TN mode does not exist between the liquid crystal layer 30 and the black matrix 22, and thus an electric potential of the black matrix 22 is affected by electric signals applied to the TFT substrate 10. In FIG. 27, the black matrix 22 is formed on the transparent insulating substrate 21, and a color filter layer 23 and an overcoat layer 27 are formed thereon.
In particular, in the transflective LCD device with the IPS mode, as shown in FIG. 27, the transmissive common electrode 18a′ and the reflective common electrode 18b′ are arranged so as to overlap with the black matrix 22, respectively. Therefore, the electric potential difference is generated between the black matrix 22 and those electrodes of the transmissive common electrode  18a′ and transmissive pixel electrode 17a, respectively. As a result, the director revolves toward the plane direct ion and causes the light leakage.
In order to resolve such problems, the patent document 3 discloses a method to apply the electric potential to the black matrix 22. In the patent document 3 the influence for the director owing to the electric potential difference is suppressed by making the electric potential of the black matrix 22 to have the same electric potential of the common electrode which is attained by applying the same signal applied to the common electrode to the black matrix 22.
That is, this patent document 3 proposes a method of applying the same electric potential as the common electrode to the black matrix in order to resolve the influence caused by the electric potential at an area where the data line and the black matrix oppose each other in the transmissive LCD type with the IPS mode However, because there are two kinds of common signals in the LCD device using the inverting drive method to be resolved by the present invention, it does not meet both of them and thus the above-mentioned problem has not been resolved.
Thus, in order to apply the electric potential to the black matrix, it needs to use such materials as the metal of the low-resistance chrome or those oxidation laminated films as the material of the black matrix 22. However, these metallic films produce the cause of the light leakage because the incident light from the  backlight exit from the transmissive area after subjected to those multiple reflections with these metallic films, the scanning line 12, the data line 13 and the transmissive common electrode 18a′. 
In order to apply the electric potential to the opposite substrate side, there is a problem that a plurality of processes should be added as disclosed in the patent document 3. In recent years, because an overcoat layer 27 is formed on the color filter layer 23 to suppress the elution of the ion component into the liquid crystal from the color filter of the opposed substrate, the overcoat layer is needed to have such additional process of forming a through hole therein in order to apply the electric potential to the black matrix.